According to the state of the art, a heat transfer loop comprises an evaporator intended to extract heat from a heat source, and a condenser intended to return this heat to a cold source. The evaporator and the condenser are connected by tubing, in which a heat-carrier fluid flows in a liquid state in the cold part of the loop and in a gaseous state in the hot part of such loop. The device of the invention relates more particularly to fluid loops in which the pumping of the heat-carrier fluid is carried out by capillarity (capillary loop). In this type of loop, the evaporator is associated with a reserve of fluid in a liquid state, and comprises a microporous mass (also called a wick) carrying out the pumping of the fluid by capillarity. The liquid-phase fluid contained in the reserve associated with the evaporator evaporates in the microporous mass under the effect of the heat originating from the heat source. The gas created in this way is discharged to the condenser, in heat exchange contact with the cold source, where it condenses and returns in liquid phase to the evaporator, in order to thus create a heat transfer cycle.
The object of the present invention relates to passive thermal regulation devices having micro capillary pumped fluid loops, intended for the cooling of heat sources such as electronic components and/or circuits. According to the state of the art, such electronic components or circuits are characterised by a small size (thickness of 1 to 2 mm, area of 10 to 100 mm2, for example) and high discharge power densities (over 50 W/cm2, for example). Furthermore, the temperature variation between the junction of the electronic component or circuit and the housing of said component or circuit is very large (by a factor of 2 to 3) compared with the temperature variation of the housing of the component or circuit and the temperature of a base plate of a board on which the component or circuit is installed.
The use of a heat transfer loop with capillary pumping to fit the size of the component or circuit, known as a micro loop, allows for the temperature difference between the junction of the component or circuit and the base plate of the board on which it is installed to be reduced advantageously, and thus for the reliability of the component or circuit to be increased by increasing the power dissipated by the component or circuit.
Such a micro capillary pumped fluid loop is characterised in that it has small dimensions (typical thickness of 1 to 2 mm, typical surface area of 10 to 100 mm2), in order to allow for it to be installed as close as possible to, or even inside, the component or circuit.
One of the limitations of heat transfer loops in operation lies in the more or less large quantity of thermal energy that is transferred to the liquid reserve through the evaporator.
A first effect of this parasitic phenomenon is the heating of the liquid flowing in the loop or contained in the evaporator reserve. A second parasitic effect is the reduction of the thermal performance of the transfer loop, which is very sensitive to the temperature of the liquid. Such a transfer loop transports almost all of the energy by phase change of the heat-carrier fluid and requires, in order to operate, several kilogram calories to keep the fluid flowing from the condenser to the evaporator in a liquid state. Even partial heating of this liquid by any means therefore very considerably reduces the heat transfer performance of the loop, and can even result in its complete stoppage.